[vsnet-grb-info 7036] GRB 081204: Swift XRT afterglow confirmation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8620
SUBJECT: GRB 081204: Swift XRT afterglow confirmation
DATE:    08/12/05 14:12:19 GMT
FROM:    Vanessa Mangano at INAF-IASFPA  <vanessa at ifc.inaf.it>

V. Mangano, B. Sbarufatti, V. La Parola (INAF IASF PA),
and W. H. Baumgartner (GSFC/UMBC)
report on behalf the Swift XRT team:

The Swift ToO observation of GRB 081204 started on 2008 Dec 4th
at 19:32 UT consists of 3.6 ks XRT exposure in PC mode.
We confirm the detection of the previously reported afterglow
candidate (Mangano et al., GRC Circ. #8616) at the refined position
RA, Dec = 349.7880, -60.2255 which is equivalent to:

RA (J2000):   23 19 09.13 
Dec (J2000): -60 13 31.7

with an uncertainty of 5.3 arcsec (radius, 90% confidence).
This is 30 arcsec from the INTEGRAL position (Gotz, GCN Circ. #8614).
The source is fading with a power law decay index of about -2,
and will reach a level of about 5.0e-4 counts/s in 24 hours
from the trigger.

The average spectrum accumulated in the time interval from
10 ks to 37 ks after the event was fitted, using Cash
statistics, with an absorbed power law. The best fit photon
index is 2.7 ± 1.5. The spectrum shows evidence of absorption
at the level of (4.4 ± 4.0)e21 cm-2, in excess of the
estimated Galactic value (1.89e+20 cm-2, Kalberla et al. 2005). 
The average observed[unabsorbed] 0.3-10 keV average flux is
about  2.7[8.5]e-13 ergs cm-2 s-1.
The count-rate-to-flux conversion factor is 1.5e-10.

All quoted errors are at 90% confidence level.

This circular is an official product of the Swift-XRT team.